You can fix this
Likely cause: debris on or around the outdoor unit
Goodman says a change in an air conditioner's sound can mean dirt or debris is getting in the way. With the power off, clear what you can reach from the outside.
Why this happens
Goodman says a rattling sound may mean the fan blade needs an adjustment or needs to be cleaned of debris, and it lists dirt or debris getting in the way of proper operation among the reasons an air conditioner's sound changes. Carrier and Bryant both tell owners to remove leaves, dirt and debris from around the outdoor unit, and Trane says to remove leaves and twigs that land on top of it. Carrier says homeowners can handle basic tasks like changing filters and clearing debris. Clearing the outside is yours. Anything inside the cabinet, the fan blade included, belongs to a technician.
How to fix it
- Set the thermostat to Off, then switch off the breaker for the outdoor AC unit. At the breaker panel, open only the hinged door, never the metal cover behind it. Carrier says to turn off the power to the AC unit before you check for obstructions around it.
- Once the fan has stopped, lift leaves, twigs and other debris off the top of the unit and pull them away from its sides and base by hand. Keep your fingers outside the fan grille.
- Trim plants back so there is at least 2 feet of open space on every side. Bryant and Trane both give that distance.
- Leave the panels and the top grille on. If something is caught inside the grille, or a fan blade looks cracked, bent or loose, keep the system off and call an HVAC technician.
- Switch that breaker back on, set the thermostat to Cool, and listen through a full cooling cycle.
When to stop. If the rattle is still there after you clear the debris, turn the system off and call an HVAC technician. Trane says a rattle is not normal and can come from a fan, the fan motor, the compressor, or a loose screw or bolt.
If this does not fix it, tell the HVAC technician
- What you cleared from the unit and whether the rattle changed.
- Whether the unit shakes or vibrates along with the rattle.
- Anything you saw through the top grille, such as a damaged fan blade or something caught inside.
- The brand and model from the outdoor unit's data plate.
Build the full list: what to tell the HVAC technician.
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